Polymerization process using nonionic surfactant and copolymerizable unsaturated polyethylene glycol

Abstract

Wholly non-charged, sterically stabilized aqueous polymer dispersions are made by emulsifying ethylenically unsaturated monomer(s) of specified slight solubility in water and subjecting them in that state to polymerization in the presence of hydrogen peroxide and a non-ionic water-soluble activator compound and also in the presence of a steric stabilizer precursor compound containing a polymer chain which is soluble in the aqueous phase and an unsaturated grouping which can copolymerize with the monomer(s). The emulsification may be assisted by a conventional non-ionic surfactant, or alternatively the precursor compound may itself possess surface-active properties.

We claim: 
     
       1. A polymerisation process in which at least one ethylenically unsaturated monomer, having a solubility in water in the range 0.08%-8% by weight but giving rise to a polymer which is insoluble in water, is emulsified in water and is subjected in that state to polymerisation in the presence of (a) a redox-type polymerisation initiator system comprising hydrogen peroxide in combination with a non-ionic water-soluble activator compound, (b) 0.5% to 10%, by weight of the monomer to be polymerized, of a conventional non-ionic surfactant and (c) 0.5 to 20%, by weight of the monomer to be polymerized, of a precursor compound the molecule of which consists of (i) a polyethylene glycol chain which has a molecular weight of 500 to 4,000 and (ii) attached to said chain at least one unsaturated grouping selected from the group consisting of methacrylate and allyl. 
     
     
       2. A process as claimed in claim 1, wherein the monomer being polymerised is such that the resulting polymer has a glass transition temperature of not more than 60° C. 
     
     
       3. A process as claimed in claim 1, wherein the non-ionic water-soluble activator compound is ascorbic acid. 
     
     
       4. A process as claimed in claim 1, wherein the hydrogen peroxide is employed in an amount of from 0.003% to 6.0% by weight, and the activator compound in an amount of from 0.01% to 7.5% by weight, based on the amount of monomer being polymerised. 
     
     
       5. A process as claimed in claim 1, wherein the polyethylene glycol chain (i) has a molecular weight of at least 1000. 
     
     
       6. A process as claimed in claim 5, wherein the polyethylene glycol chain (i) is derived from a polyethylene glycol, or a monoalkyl ether thereof, in which the alkyl group contains from 1 to 4 carbon atoms. 
     
     
       7. A process as claimed in claim 6 wherein the polyethylene glycol chain (i) is derived from a polyethylene glycol, or a monomethyl ether thereof, of molecular weight in the range 2000-4000. 
     
     
       8. A process as claimed in claim 7, wherein the precursor compound is the methacrylic acid ester of the monomethyl ether of polyethylene glycol, mol.wt. 2000. 
     
     
       9. A process as claimed in claim 1, wherein there is present, in an amount of from 0.1% to 2% by weight of the monomer taken, a water-soluble chain transfer agent. 
     
     
       10. A process as claimed in claim 1, wherein the monomers to be polymerised include a reactive monomer selected from glycidyl acrylate, glycidyl methacrylate and γ-methacryloxypropyltrimethoxysilane. 
     
     
       11. A sterically stabilised aqueous dispersion of polymer obtained by a process as claimed in claim 1. 
     
     
       12. A sterically stabilised aqueous dispersion of polymer obtained by a process as claimed in claim 1.